Breaking down the 2012 NBA Offenses: Looking for Floor Stretch

It is easier to perceive error than to find truth, for the former lies on the surface and is easily seen, while the latter lies in the depth, where few are willing to search for it.

-Johann Wolfgang Von Goethe

You’ll know it when you see it.

For the last while we have been having an ongoing conversation amongst the contributors for this site about the specific value of position (You can read Ari’s thought provoking piece on this here). As is typical of the truly great pieces that we are lucky to have in this space, it has inspired some interesting avenues of thought for me.

One such avenue was also inspired by the videocast with our own Andres, Vivek and Hoospeak‘s Beckley Mason. In it, Beckley asked a question about the Memphis Grizzlies in the 2011-12 NBA Season. The Grizzlies led the league in offensive rebounds plus steals per game and both of these generally create easy buckets. So, why then are the Grizzlies only at 19th in Offensive ranking (as measured by points per 100 possessions)?

The easy answer seems to be that they shoot poorly as evidenced by their poor Effective Field Goal percentage and it matches what we see for Memphis and Sacramento. The problem is that it doesn’t completely hold for Utah, Milwaukee and Indiana who are not great shooters but do actually rank in the top ten in offense. This lead me to take a deeper look.

Thanks to the wonderful Hoopdata site I was able to look at shotcharts for every team and take this a lot further. Let’s start with the breakdown by position:

That gives you the shot percentage of total by distance from the rim. The picture is a little more clear once you add in the actual efficiency.

The Worst return at the rim was 57% for the Nets (1.14 points per shot), the worst from three was 44% for the Bobcats (.88 points per shot). The best from 3-9 feet,10-15 feet or 16 to 23 feet was 43% for Miami (.86 points a shot). It seems then that to be efficient we want to shoot from the rim or from three and minimize the % of shots from 3-23 feet (or as a colleague once called them “Shit” shots).

How does this help our quest? Turns out the Grizzlies despite stealing and rebounding their way to 22.2 easy opportunities a game tend to lose the plot. I am reminded of something I wrote after their Game #4 loss versus the clippers in the playoffs last year:

Gay makes the first moonshot. Bledsoe and Evans make 1 of 4 fts. Gay makes another. LAC by one 9 ticks left.

Bledsoe is choking, somebody help him. Memphis hc set to the rescue and the clippers win.

Timeline over. What did we learn? Memphis is atrocious in 4th quarter play calling. LAC goes for high value offense. This is important.

Let’s recap, Memphis tends to focus on low value offense as their default. They rank 5th in shit shots % and 21st in efficiency from that range and they also rank 28th in threes as a % shots and 25th in efficiency from that range. Practically, this means that if you clog the lane and force them into a halfcourt offense, they’ll effectively beat themselves by taking contested jumpers from inside the three point line. This then neutralizes their outstanding post bigs and turns their offense into a series of head-shaking heroball possesions.

You could say that their lack of floor stretch kills what should be an effective offense.

Let’s lay this out in another fashion.

When we look at teams by offensive rank and by % by region and efficiency we start to see some real evidence of the floor stretch phenomenon. I don’t think it an accident that the top three teams in offensive efficiency are all towards the bottom of the Shit shot takers and at top of shots at the rim and from three. Interestingly, San Antonio, OKC and the Clipps all are efficient at the shit shots they do take perhaps as a function of the space created. The bottom of that list is also top heavy with shit shot takers and not three point shooting teams.

The lesson to be learned? A simple one is that no team,I repeat NO team,should be taking less than a quarter of their shots from three. Let’s take Memphis as an example. If they exchanged shit shots for threes until they had 25% from long range they would increase their point per 100 possession by 2.1 without accounting for the probability that it would help their percentages at the rim and other ranges by stretching the defense and giving them additional open looks. 2.1 pts is good enough for about 2.1/31.1*82= 5.5 wins. So five and a half extra wins just from taking more threes.

And before anyone starts about how shooting more from three is going to drive down field goal efficiencies, I looked (see here for the really cool interactive chart). In the last twenty seasons, Three point attempts per game are positively correlated with three point field goal percentage, effective field goal percentage, points per 100 possessions and two point field goal percentage.

The actual results are shown below:

Trend Lines Model

A linear trend model is computed for sum of 3PA per game given sum of 3pt Fg %. The model may be significant at p <= 0.05.

Model formula:

( 3pt Fg % + intercept )

Number of modeled observations:

582

Number of filtered observations:

0

Model degrees of freedom:

2

Residual degrees of freedom (DF):

580

SSE (sum squared error):

8180.07

MSE (mean squared error):

14.1036

R-Squared:

0.199361

Standard error:

3.75547

p-value (significance):

< 0.0001

A linear trend model is computed for sum of 3PA per game given sum of EFG%. The model may be significant at p <= 0.05.

Model formula:

( EFG% + intercept )

Number of modeled observations:

582

Number of filtered observations:

0

Model degrees of freedom:

2

Residual degrees of freedom (DF):

580

SSE (sum squared error):

8158.18

MSE (mean squared error):

14.0658

R-Squared:

0.201504

Standard error:

3.75044

p-value (significance):

< 0.0001

A linear trend model is computed for sum of 3PA per game given sum of 2P Fg%. The model may be significant at p <= 0.05.

Model formula:

( 2P Fg% + intercept )

Number of modeled observations:

582

Number of filtered observations:

0

Model degrees of freedom:

2

Residual degrees of freedom (DF):

580

SSE (sum squared error):

9506.8

MSE (mean squared error):

16.391

R-Squared:

0.0695048

Standard error:

4.04859

p-value (significance):

< 0.0001

A linear trend model is computed for sum of 3PA per game given sum of Pts per 100 possesions. The model may be significant at p <= 0.05.

21 Responses to "Breaking down the 2012 NBA Offenses: Looking for Floor Stretch"

“In the last twenty seasons, Three point attempts per game are positively correlated with three point field goal percentage, effective field goal percentage, points per 100 possesions and two point field goal percentage.”

So teams that shoot a lot of threes are good at shooting. That means that if my team starts shooting more threes, they will become better at shooting!!

If there is one thing that would consistently improve the (already high) quality of the posts on wages of wins it would be to stop and ask yourselves, before each post, whether the causation could run the other way, or even in both directions. There would be less “our research shows players who shoot more are better at shooting, therefore volume effects are a myth”…

As a Griz fan I am genuinely interested to see whether an improved three point attack does flow through to the rest of the offence. Fingers crossed.

Rudy Gay plays a lot of hero ball. Zach Randolph goes through spells where he drifts from the block and shoots a ton of fadeaways. Gasol lingers in the high post and will shoot from there if left alone. And Tony Allen sometimes has the ball at the end of the shot clock for reasons I can’t fathom and takes those long 2s. That’s just the starters. With Randolph out most of last year Speights took a ton of long 2s.

So far they don’t seem to have taken your advice. They are towards the bottom of the league in 3s (though they killed it from 3 last night against the Heat). They are 10th in 16-23 feet attempts and 3rd to last in both attempts at the rim and FG% at the rim. Small sample size. But it looks like they are 5th points per game because they are just getting more possessions, 7th in pace.

A quick and dirty fix would be to show that the effects would hold true given no change in FG% from 3. As simple as that. If you can show that simply volume increase would = win increase, you wouldn’t fall in this
“more 3s = more efficient 3s” causation/reverse causation trap.I believe this would be simple arithmetic. Current 3 * 3FG%*(currentFGA+new3FGA) – 2FG%*(new3FGA). If this = +oRTG and eFG. Point proven, job done. Everyone’s happy.

Let’s say I’ve instructed my good 3-point shooters to launch 3’s anytime those shots are open. Assuming the team follows my instructions, subsequently asking them to increase the % of 3-point shots they take (i.e. shooting 3’s when that shot is not open) will lead to a lower 3-point shooting percentage (assuming defense matters at all).

All,
I want to respond to what I see as a misconception. I am not suggesting that more taken three’s equal a better 3fg%. I am fully aware that there’s a very definite multicolinearity at work here. Teams with better shooter will tend to take more outside shots. However the data does strongly suggest that within the observed rate of 3fga per game there seems to be no tradeoff in efficiency from increased attempts. So if even the team with the worst 3fg% should see a marginal increase on points scored from increasing 3pa at the expense of long two’s then everyone should be moving in that direction.

In essence, I am saying that current offensively philosophy is leaving points on the table willingly.

Ah, So what you are saying Arturo, is that given your data, plugging the numbers into my formula nets in a positive result! Good, I’m convinced then. If the effect that Tommy is suggesting doesn’t seem to be at play, then all is sound and logical. Bomb away Rudy, bomb away.

I think this is why a guy like Scola is trying to become a 3 point shooter, because teams know this about threes, and are moving towards more and more 3s, especially in the corner.

I think that is why Nash is such an efficient player – last year the Suns, with practically no good players and the worst bench i have ever seen, were 9th in the league in efficiency, because Nash gets other players layups and threes, and when he shoots, he makes an efficient number of shots from almost everywhere or gets a layup.

Good post. I think if you compare Mike Conley’s shot selection this season (so far) vs last season, you will see some evidence of change in Grizzlies coaching philosophy re the 3 ball. There is still the problem with correlation/causation as the team specifically brought in shooters to address this problem, but Conley has been a constant so his performance should be a reasonable marker for the value of taking more 3 fga. See @flyergrizblog for additional (and more insightful) input.

@Tommy, If your “good shooters” are taking long 2’s currently they are almost certainly contested. The vast majority of long 2’s come when someone is trying to drive to the basket and can’t get past their defender then takes a step-back or fade away jumper. Or tries to post-up and can’t get into the paint.

I have no numbers for what the percentage of wide open long 2’s is, but I would be surprised if it is above single digits. It happens on occasion that no one rotates to the ball either because of a communications breakdown on the defense or because the defense is willing to let a horrible shooter take an open 2 while they worry about rebounding position, but that is usually only 1-2 times per game.

I don’t think most perimeter players in the NBA suffer a 33% drop in shooting percentage going from 18 to 23 feet. So while defense matters, it is still a better strategy to take a contested 3 than take a contested 2.

“However the data does strongly suggest that within the observed rate of 3fga per game there seems to be no tradeoff in efficiency from increased attempts.”

Your data can only show this if it is some kind of random sample, rather than a series of optimised equilibria. As I say, this is an ongoing problem, and I’m pleased to see the recent attempts to introduce some game theory into WoW.

I’ve followed this blog from It’s very beginning. This is the best article to date, and represents the most “out of the box” thinking you guys have done yet. This will go a long way towards real world application of the wins produced model. Nice to see a departure from “If it hasn’t been measured it doesn’t exist.”

@Joe, it sounds as though you agree that a wide-open 2-point shot, even a long one, is generally wiser than a contested 3. Your point is that wide-open 2’s are rare. Understandibly, you don’t have the %. But, to evaluate the core argument, one needs that percentage. The hypo was built to illustrate this need, rebutting Kai’s (not-entirely-serious) assertion: “Point proven, job done.” (note the tense)

Teams should tell good shooters (Ray Allen, Steph Curry, Danny Green, Steve Novak) to attempt more 3s
Unless when, by so doing, these shooters exchange wide-open 2s for contested 3’s
Which would certainly occur sometimes but we can’t (yet) say how often
So, if it occurs rarely then… cool! If it occurs often then… nevermind. As you were.

Assuming Joe is right and the percentage is less than 10: Awesome. Make it rain. But until we know that %, the point is unproven and the job is unfinished.

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